1. Field of the Invention
The present invention relates to a simulation device and method of simulating the current flowing in an electronic device using a moment method. More particularly, the present invention relates to a simulation device and method for performing accurate simulation of an electronic device having an amplifier, and a computer readable storage medium encoded with processing instructions for implementing a simulation method to simulate the current flowing in an electronic device.
2. Description of the Related Art
Society has demanded that the radiation of radio waves and noise by electronic devices not be above a certain level, and countries throughout the world have regulations strictly controlling the levels of radio waves and noise. A variety of technologies are employed to comply with the various types of regulations concerning the level of radio waves, such as shield technology and filter technology. To quantitatively calculate the degree to which these technologies reduce the level of radio waves, the development of simulation technology is necessary.
Furthermore, society has demanded that electronic devices not be affected by radio waves radiated by other electronic devices and which are below a certain level, and countries throughout the world have regulations strictly controlling these levels. To comply with these regulations concerning radio waves, it is checked whether electronic devices are affected by the radio waves radiated by antennas. Therefore, what is needed to satisfy the various regulations is simulation technology to simulate the effect of radio waves radiated by antennas on electronic devices.
In order for the simulation technology to be practical, it is necessary to provide technology that performs accurate simulation processing. In view of the need for accurate simulation technology, the present inventors have disclosed simulation technology which uses the moment method to simulate the current flowing in electronic devices.
The electrical and magnetic currents flowing in electronic devices can, theoretically, be obtained by solving Maxwell's electromagnetic wave equations under given boundary conditions. The moment method is one method of solving integral equations derived from Maxwell's electromagnetic wave equations. More particularly, the moment method is a method of performing calculations of electrical and magnetic current by partitioning a body into small elements, and can be applied to three-dimensional bodies of any shape. The moment method is disclosed, for example, by H. N. Wang, J. H. Richmond and M. C. Gilreath, “Sinusoidal Reaction Formulation for Radiation and Scattering From Conducting Surface,” IEEE Transactions Antennas Propagation, vol. AP-23, 1975.
The moment method translates the structure of the electronic device to be simulated into a mesh and selects the frequency to be processed. The frequency to be processed is found by performing a predetermined calculation on the mutual impedance, mutual admittance and mutual reactance between the elements that have been translated into the mesh. By substituting the mutual impedance, mutual admittance and mutual reactance thus found and the wave source designated by the structural information into the simultaneous equation of the moment method and solving the equation, the electrical current and magnetic current flowing in each element can be found.
In other words, when a metallic object is concerned, the metallic portions are translated into a mesh in order to perform analysis. Mutual impedance Zij between the meshed metallic elements (the value at the processing frequency) is found, and by solving the following simultaneous equation of the moment method formed between the mutual impedance Zij, the frequency component wave source Vi and current Ii flowing in the meshed metallic elements is determined.[Zij][Ii]=[Vi], with [ ] being a matrix
The intensity of the electromagnetic field being radiated by an electronic device is calculated from the result of the above equation.
Mutual impedance displays the relationship between the electrical field caused by the electric current of one element and the electric current of other elements. Mutual admittance, which is necessary when considering the presence of a dielectric substance, displays the relationship between the magnetic field caused by the magnetic current of one element with the magnetic current of other elements. Mutual reactance, which is necessary when considering the presence of a dielectric substance, displays the relationship between the electric field (or magnetic field) caused by the electric current (or magnetic current) of one element and the electric current (or magnetic current) of other elements. As described herein, electric currents flow in metals, and electric currents and magnetic currents flow on the surface of dielectric substances.
When using the moment method to simulate the electric current and magnetic current flowing in an electronic device with the conventional technology, if the electronic device has an amplifier, the electric current and magnetic current flowing in the electronic device are simulated by hypothesizing a wave source that generates a voltage equivalent to the voltage input into the amplifier at the amplifier's input terminal, and by hypothesizing a wave source that generates a voltage equivalent to the voltage output by the amplifier at the amplifier's output terminal.
However, when using the conventional technology, there is a problem of not being able to accurately simulate the electric current and magnetic current flowing in an electronic device. In particular, the voltage and current input into an amplifier will vary depending on radio waves from external sources and radio waves from the other circuit elements in the electronic device, and the voltage and current output by the amplifier will vary according to the input voltage and current as affected by the radio waves from external sources and internal circuit elements. The conventional technology does not use a model which takes into account radio waves from external sources and radio waves from other circuit elements, resulting in the problem of not being able to accurately simulate the electric current and magnetic current flowing in an electronic device.
Furthermore, with the conventional simulation technology, when the electronic device to be simulated has an amplifier, a model of an amplifier is made with two wave sources independent of each other (i.e., a wave source disposed on the input terminal of the amplifier and a wave source disposed on the output terminal of the amplifier). Moreover, even if the voltage and current input at the amplifier vary because of the radio waves from an external source or the radio waves from the other circuit elements of the electronic device, the voltage and current output from the amplifier will not vary. Thus, an accurate simulation of the electric current and magnetic current flowing in an electronic device cannot be made.